In the design and construction of architectural structures, it is a common practice to provide for segmented construction, with a space being provided between adjacent structural units, which may be relatively movable with respect to each other as a result of normal expansion and contraction, and in some cases as a result of seismic activity. It is typical, in such structural arrangements, to provide a suitable cover means for spanning the gap between the adjacent structures. Such cover arrangements typically may include a cover plate which extends across the gap between the adjacent structures and is movably received with respect to one or both of the structures, frequently in a recess or chamber provided therein. In many cases, facilities are provided for maintaining the cover plate in a centered or symmetrical relation to both of the adjacent architectural units.
In one well known form of expansion joint system of the general type described above, a generally flat cover plate extends across the space between two adjacent structural units and projects slidably into a cavity in at least one of them. As the two structures are caused to move toward and away from each other, the cover plates slides into and out of a recess provided to receive it. Examples of known designs of such joint systems are reflected in the Balzer et al. U.S. Pat. No. 3,371,456 and the Hallock U.S. Pat. No. 3,417,528, for example.
Where the movement to be accommodated by the expansion joint system is purely a function of normal expansion and contraction, a conventional joint system of suitable proportion can provide adequate performance. Where occasional seismic activity must be accommodated, however, the joint must be designed for significantly greater than normal motion on at least an occasional basis. To accommodate such exceptional occasional motion with joint systems of conventional design requires joint systems that are undesirably large in relation to the normal separation between the adjacent structural units. This is not only costly but, perhaps equally important, tends to be aesthetically unattractive.
In accordance with the present invention, a novel and improved architectural joint system is provided which incorporates multiple stages of expansion, by reason of a telescopic construction. During normal expansion and contraction activities, the new joint system has the appearance and function of systems of more conventional design. However, when, due to seismic activity or other reasons, the normal separation of the structures is exceeded, the joint system of the invention is capable of expanding accordingly, through a second stage expansion feature. The new joint system thus accommodates a substantially greater degree of separation between the structural units, without at the same time requiring the components of the joint system to be undesirably wide. The joint system of the invention is especially well suited for use in walls and ceilings, while not being limited thereto.
In a preferred form of the invention, an otherwise conventional sliding cover plate is received within normally stationary but telescopically movable sleeves, which are in turn slidably received within chambers defined by the stationary structure of the expansion joint system. During normal expansion and contraction, the cover plate slides with respect to the telescoping sleeves to accommodate normal motion. When the separation of the structural unit exceeds the width of the cover plate, however, the telescoping sleeves themselves slide within the mounting structure, to greatly increase the ability of the structures to separate without destroying the expansion joint system.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments of the invention and to the accompanying drawings.